This invention relates generally to image scanning, and specifically to such systems which effect color masking.
Color copying has become increasingly important in recent years because of changes in public acceptance of, and demand for, color information. The pressures created by these demands have resulted in numerous technological advances in the color reproduction arts, among which is that set forth in the instant disclosure.
Due to the inability of readily available and economic dyes to adequately transmit colors, it is necessary that some compensation or color correction be made to reduce the amount of specific pigments in specific areas--a compensation which is most often accomplished by the process known as color masking. Many color masking techniques are known in the art as, for example, those described in The Focal Encyclopedia of Photography, Vol II, pp. 921-927, W. & J. Mackay & Co., Ltd., Chatham, England, 1965, or by Yule in Principles of Color Reproduction, John Wiley & Sons, Inc., New York, 1967. These techniques include the well-known photographic process of masking color separation negatives or positives, with other negatives or positives to vary the density of the specific color components.
Additional related techniques include the use of electronic color scanners which simultaneously or individually produce color separations. These devices scan the subject along very narrow lines using a small light beam and, through lenses and electronic gear obtain all of the information needed to separate colors and make such corrections as necessary. Many of these devices are known in the art, a brief summary of which is set forth by Yule, supra, pages 305-326.
The instant invention makes use of a broad class of imaging members which record optical images by an image-wise distribution of photo-generated voltages or current acting upon a voltage or current-alterable recording medium. Typically, in these members, imagewise activating radiation incident on a photoconductor allows charge carriers to move in an external electrical field. These charge carriers interact with a voltage or current-sensitive member which in turn modulates light in the form of a phase image.
U.S. Pat. No. 2,896,507, describes an imaging member which includes a photoconductive layer on an elastically deformable layer sandwiched between a pair of electrodes, one of which is a thin metallic layer overlying the deformable layer. In operation, imagewise activating radiation is directed upon the member and an electrical field is established across the photoconductive and deformable layers thus causing these layers to deform in image configuration. The member is described as being capable of functioning as an image intensifier since the deformation image may then be read out with a high intensity light source and a Schlieren-type optical system.
Recently, a major advance in the art was made by Sheridon who disclosed the Ruticon (derived from the Greek words "rutis" for wrinkle and "icon" for image) family of imaging members wherein the voltage-sensitive light-modulating recording medium comprises a deformable elastomer layer and a photoconductive material may be provided as a separate layer or incorporated in the elastomer layer. For a detailed description of the Ruticon devices, see IEEE Transactions On Electron Devices, Sept. 1972, and U.S. Pat. No. 3,716,359. Various different embodiment for establishing an electric field across the elastomer layer are described.
Referring now to FIG. 1, an exemplary imaging member from the Ruticon family is shown. Many modifications of the elements are known in the art, but generally imaging member 1 is comprised of a substrate 6 which is a transparent non-conductive layer having thereon a conductive transparent layer 5. Layer 4 is a photoconductive material which will allow the passage of more electrical charges into these regions which are exposed to light. Elastomer 3 may be of a class of elastomeric solid materials including both natural, such as natural rubbers and synthetic polymers which have rubber-like characteristics, i.e., elastic, and include material such as styrene-butadiene, polybutadiene, neoprene, butyl, polyisoprene nitrile and ethylene propylene rubbers.
A thin continuous conductive layer 2 is placed on the surface of the elastomer, and is flexible enough to follow the deformations of the elastomers. In a preferred embodiment, this layer is also highly reflective.
Power supply 7 provides D.C. voltages of one polarity to form a deformation image on the surface of the elastomer. The polarity required depends primarily on the nature of the photoconductor. Power supply 7 must be capable of being turned off to erase the image, or undergo a shift in polarity to more rapidly erase the image. Supply 7 may also be A.C. or a combination of an A.C. and D.C.. The external electrical circuit may also include suitable switching means (not shown). Also, not shown, is an optional floodlight which may facilitate erasure and an absorption-type line grating, usually positioned between the substrate and the photoconductive layer.
This layer of image recorder can be read out using Schlieren-type optics. The positive image will be produced by diffracted light (higher orders), and the negative image will be produced by the undiffracted light (zero order).
The above-described Sheridon patent and copending application to Bergen, described below, disclose several embodiments of electro-optical image recorders, several variations upon their useful application and several useful modifications of a color scheme. The instant invention employs these teachings in a novel fashion to achieve results comparable to prior art color masking techniques.